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Teaching Computing…

Teaching Computing…. …to GCSE Level with Python Sue Sentance Sue.sentance@ anglia.ac.uk. Course overview. Available specifications for 2012-2013. OCR – will be in third year EdExcel – now delayed until September 2013 AQA – up and running from September 2012

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Teaching Computing…

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  1. Teaching Computing… …to GCSE Level with Python Sue Sentance Sue.sentance@anglia.ac.uk

  2. Course overview

  3. Available specifications for 2012-2013 OCR – will be in third year EdExcel – now delayed until September 2013 AQA – up and running from September 2012 Behind the Screen – E-Skills work-in-progress to create a GCSE in Computer Science

  4. OCR GCSE Computing 3 units A451 – Theory (Examination) A452 – Practical investigation (Controlled Assessment) A453 – Programming (Controlled Assignment)

  5. AQA Computer Science Component 1 – Practical programming 50 hours controlled assessment Worth 60% Component 2 – Computing fundamentals 1 ½ hour examination Worth 40%

  6. Today’s session 4:45 – 5:45 Binary & Binary arithmetic/ Hex 6.00 – 7.30 Starting to program in Python

  7. From the specification OCR • (a) define the terms bit, nibble, byte, kilobyte, megabyte, gigabyte, terabyte • (b) understand that data needs to be converted into a binary format to be pro • (c) convert positive denary whole numbers (0-255) into 8-bit binary numbers and vice versa • (d) add two 8-bit binary integers and explain overflow errors which may occur • (e) convert positive denary whole numbers (0-255) into 2-digit hexadecim AQA • understand that computers use the binary alphabet to represent all data and instructions • understand the terms bit, nibble, byte, kilobyte, megabyte gigabyte and terabyte • understand that a binary code could represent different types of data such as text, image, sound, integer, date, real number • understand how binary can be used to represent positive whole numbers (up to 255) • understand how sound and bitmap images can be represented in binary • understand how characters are represented in binary and be familiar with ASCII and its limitations • understand why hexadecimal number representation is often used and know how to convert between binary, denary and hexadecimal

  8. Binary numbers 0

  9. Binary numbers 1

  10. Learning binary numbers Converting binary to denary Converting denary to binary Binary addition

  11. Storing Binary Numbers Inside the computer eachbinarydigit is stored in a unit called a bit. A series of 8 bits is called a byte. A bit can take the values 0 and 1

  12. What is meant by? 1 byte ? 1 nibble ? 1 kilobyte ? 1 megabyte ? 1 gigabyte ? 1 terabyte ?

  13. Storing data 1 byte 1 nibble 1 kilobyte 1 megabyte 1 gigabyte 1 terabyte 1 byte = 8 bits 1 nibble = 4 bits 1 kilobyte = 1024 bytes = 2 10 bytes 1 megabyte = 2 20 bytes = 210 kilobytes 1 gigabyte = 2 30 bytes = 210megabytes 1 terabyte = 2 40bytes = 2 10 gigabytes

  14. ActivityBinary counting exercise

  15. How to convert Binary Numbers to denary 128+0+0+16+8+ 0+ 2 +1 = 155 in Denary Place values 128 64 32 16 8 4 2 1 1 0 0 1 1 0 1 1

  16. Storing Numbers - Binary EXAMPLE Convert the binary number 1011 0111 into denary: Answer 128 64 32 16 8 4 2 1 1 0 1 1 0 1 1 1 =128+32+16+4+2+1=183

  17. Conversion Exercise Convert the following binary numbers into denary: 0 0 1 0 1 0 1 0 0 0 1 0 0 1 1 0 1 1 1 0 1 0 1 0 1 1 1 1 1 1 0 0 1 0 1 0 1 1 0 1 1 1 1 1 1 1 1

  18. Teaching binary Holding cards up activity Finger binary Cisco binary game CS Unplugged actitivies

  19. Converting Denary to Binary • Write down the column headings for the binary number:64 32 16 8 4 2 1 • Process each column from left to right. • If the denary number to be translated is greater than or equal to the column heading, place a 1 in the column and subtract the value of the column from the denary value. • If the denary value is smaller than the column heading, place a 0 in the column.

  20. Convert to Binary 3 5 8 7 11 16 32 21 14 17 48 255

  21. Sizes of Binary Numbers • If we have 4 bits available the largest number is 1 1 1 1 (which is 15 in denary) • If we have 5 bits available the largest number is 1 1 1 1 1 (denary value 31) • If we have 7 bits available the largest number is 1 1 1 1 1 1 1 (denary value 127) • If we have 8 bits available the largest number is1 1 1 1 1 1 1 1 (denary value 255) • Can you see a pattern? animated

  22. To calculate the max size • In general if we have n bits available then the largest denary number we can store is 2n - 1 • For example, for 3 bits, 1112 = 23 – 1 = 8 – 1 = 7

  23. Addition Rules for Binary 0 + 0 = 0 1 + 0 = 1 0 + 1 = 1 1 + 1 = 10 (write down 0 and carry 1) 1 + 1 + 1 = 11 (write down 1 and carry 1)

  24. Adding Binary Numbers add 8 and 5 8 1 0 0 0 5 0 1 0 1 ---------------- 13 0 1 1 1 check the answer using place values: 8+4+0+1 = 13

  25. Adding Binary Numbers add 9 and 5 9 1 0 0 1 5 0 1 0 1 ---------------- 1 carry 14 1 1 1 0 check the answer using place values: 8+4+2+0 = 14

  26. Exercises – see sheet

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